A semiconductor laser device is highly effective in converting electrical input into laser oscillation output. The advantage has increased the needs for using the semiconductor laser device for an excitation light source of a solid-state laser or a direct process light source.
The manufacturers of the semiconductor laser device have introduced a semiconductor laser bar—in which a plurality of emitters (emitting sections) is formed in a one-dimensional arrangement—to the market. To easily use laser light emitted from the emitters for the excitation light of a solid-state laser or a processing purpose, a method in which the laser light is connected to an optical fiber is well known (see Patent Literature 1, for example).
FIG. 12 shows a conventional semiconductor laser device. The semiconductor laser device has semiconductor laser element 101 for emitting laser light, heatsink 102 for cooling semiconductor laser element 101, and metallic plate 103. Before fixing metallic plate 103 to heatsink 102, electrical isolation has been provided between them.
Metallic wire 104 has bonding connection with semiconductor laser element 101 and metallic plate 103, providing electrical connection between semiconductor laser element 101 and metallic plate 103. Electrode plate 106 provides the inside of package 105 of a box shape with electric power.
Further, insulating member 107 provides electrical isolation between package 105 and electrode plate 106. Metallic member 108 connects between metallic plate 103 and electrode plate 106. Rod lens 109 collimates the laser light emitted from semiconductor laser element 101. Rod lens 109 is held by lens fixing base 110.
Fiber array 111 is formed of a bundle of optical fibers for guiding the laser light collimated by rod lens 109 to outside package 105. Optical fiber 112 guides the laser light to outside package 105.
Package 105 is sealed with lid 113. Sealing member 114 provides hermetically sealed condition between package 105 and lid 113. Sealing member 115 provides hermetically sealed condition between package 105 and optical fiber 112.
The operations of such structured semiconductor laser module will be described.
Electrical power input fed from a power supply device is brought, via package 105 and heatsink 102, to the anode side of semiconductor laser element 101, and further, the input is brought, via electrode plate 106, metallic member 108, metallic plate 103, and metallic wire 104, to the cathode side of semiconductor laser element 101. Receiving the electrical power input, semiconductor laser element 101 outputs laser light.
The laser light from the semiconductor laser element is collimated by rod lens 109 and injected into fiber array 111. Guided by optical fiber 112 to the outside of package 105, the laser light is used as excitation light for a solid-state laser or as a direct process light source.
In response to electric power supply, semiconductor laser element 101 offers laser oscillation through electrical/optical conversion. At the same time, an amount of the electric power is consumed by a resistance component of semiconductor laser element 101, by which heat is generated. In addition, laser light and the scattering light is partly absorbed. As a result, the inside of package 105 has increase in temperature.
To avoid the temperature rise caused by the heat generation, an attempt has been made. That is, the bottom of package 105 is cooled by a cooling medium or a Peltier device so as to cool down heatsink 102, semiconductor laser element 101, and the inside of package 105.
According to a conventional semiconductor laser device, however, the higher the power of semiconductor laser element 101, the larger the electric power input; at the same time, the larger the amount of heat generation. Due to lack of cooling capacity of the semiconductor laser module, the case of semiconductor laser element 101 increases in temperature, thereby degrading reliability of semiconductor laser element 101. Besides, the temperature rise inside package 105 can invite position variation of rod lens 109, thereby degrading the beam quality.